DONORS.

TITLE OF work.

Mylne, R. W. Section of the well sunk at the Bank of

England.

Pupils and Assistants of the President. Portrait (framed) of J. M. Rendel (President).

Rickman, W. Portrait of the late G. B. Maule, Assoc. Inst. C. E.

Shelley and Treppass, Messrs. The Trihedral view of the Palace for the Exhibition of the Industrial products of Mankind.

Simpson, J. Copies of six Drawings of engine, boiler, pumps, pipes, reservoirs, &c., for the York Water Works, 1781 to 1785. By J. Smeaton, Civil Engineer.

MAPS.

Meikleham, E. Map of the country for ten miles round Glasgow. By E. Meikleham.

Mylne, R. W. Topographical Map of London, and its environs: coloured geologically. By R. W. Mylne.

OFFICERS.-1853.

COUNCIL.

PRESIDENT.

JAMES M. RENDEL, F.R.S.

VICE-PRESIDENTS.

ISAMBARD K. BRUNEL, F.R.S. | JAMES SIMPSON, F.G.S. JOSEPH LOCKE, M.P., F.R.S. ROBERT STEPHENSON, M.P.,

JAMES WALKER, F.R.S., L. & E. | SIR JOHN RENNIE, F.R.S.

JOSHUA FIELD, F.R.S.

HONORARY COUNSEL.

CHARLES F. F. WORDSWORTH.

SIR WILLIAM CUBITT, F.R.S.

HONORARY SOLICITOR.

WILLIAM TOOKE, F.R.S.

HONORARY ARCHITECT.

THOMAS HENRY WYATT, F.R.I.B.A.

January 11th, 1853.

JAMES MEADOWS RENDEL, President,

in the Chair,

THE following candidates were balloted for, and duly elected :Stephen Collins Court, as a Member;-Edward Bagot, John Hodgson, and Arthur Sinclair, as Associates.

No. 881." On the Nature and Properties of Timber, with descriptive particulars of several methods, now in use, for its Preservation from Decay." By HENRY POTTER BURT,

Assoc. Inst. C.E.1

TIMBER, by which is understood all the descriptions of wood, both of foreign and home growth, which are used for engineering, shipbuilding and architectural purposes, is an article of such immense importance, and enters so largely into works of all kinds, that an essay upon its history, peculiarities, uses, and preservation, can scarcely fail to be an interesting subject of inquiry, and the Author, whilst endeavouring to explain the views and observations, deduced from many years' experience, may reasonably hope, that, however imperfect, his efforts may be useful, in exciting a discussion worthy of the Institution, and in eliciting facts and details which will prove beneficial to the profession.

An inquiry into the history, cultivation, physiology, and properties, of timber, is of more than ordinary interest, not only on account of its almost unlimited application in construction, but in a commercial point of view, and it is likewise of great national importance, as having been the subject of fiscal regulations which, at one period, produced a large addition to the revenues of the kingdom; it is thus of sufficient importance to claim the attention of the political economist, the capitalist, and the consumer, as well as that of the civil engineer.

1 The discussion upon this paper extended over portions of three evenings, but an abstract of the whole is given consecutively.

The peculiarities of timber, and its value for general purposes, embrace so wide a field for inquiry and observation, that it would be impossible, in the limits of this paper, to do more, than enter briefly, into the more important and useful bearings of the question,-sketching, as it were, a skeleton diagram of the subject, which others, having leisure and opportunity, may hereafter render complete.1

Historically, timber seems to have been naturally the earliest material known for construction-and shipbuilding one of its first recorded applications, for under Divine instruction, Noah "made himself an ark of gopher wood," (Gen. chap. vi. ver. 14.); and throughout the sacred volume, innumerable other instances occur of the use of timber, for the purposes of the artificer, in every branch of construction, whilst the Egyptian mummy cases and the utensils discovered at Nineveh, show that the early artisans must not only have been acquainted with mechanical contrivances, but must, also, have well understood the selection of those sorts of wood, which were of the most enduring character, and the least susceptible of decay.

In the ecclesiastical and castellated ruins of our own country, there are many existing proofs of the early use of timber; and some of the most interesting relics of antiquity, such as King Arthur's round table at Winchester, the coronation chair, and the doors of the inner chapel at Westminster Abbey, and many other specimens of great interest still existing in many parts of the kingdom, not only exhibit considerable skill in the artificer, but testify that the timber of our own island, yields to none in point of strength, and enduring qualities.

Chemically considered, the ultimate elements of wood consist of carbon, oxygen, and hydrogen, but it may more proximately be described as a compound of woody fibre, starch, gum, sugar, and vegetable acids,-these form the constituents of all the organs of a tree and are essential to its existence, and it would appear that on the varying proportions of these constituents, many of the peculiarities and much of the strength and durability of timber must depend.

1 This subject is extremely well treated in the article "Wood," partly abridged from papers by Professor Forbes, and published in "Tomlinson's Cyclopædia of Useful Arts."- EDITOR.

Chemical transformation, or in other words-decomposition, putrefaction, and decay, must form an essential part of this inquiry; and the nature, action, and results of these changes shall be briefly examined.

Woody fibres and all organic compounds, when in contact with other bodies, are liable to certain changes tending towards decomposition. There are two distinct modes in which these changes take place;-the first is, when the decomposition is effected by the agency of a body, which unites with one, or more of the constituents of the compound, and by this union causes the remaining elements to enter into a new form. In the second mode, the chemical affinity of the acting body causes the component parts of that acted on to combine with it.

A body, in the act of decomposition, exercises an influence upon any other body, with which it may be in contact, in the same manner that a body in the act of combustion inflames another combustible body, in its vicinity. In organic nature, besides those processes of decomposition, termed fermentation and putrefaction, another and not less striking class of change occurs in bodies exposed to the influence of the air; this is the act of gradual combination of their combustible elements-with the oxygen of the air-a slow combustion, or oxidation, to which the term eremacausis is usually applied, the conversion of wood into humus is one of the numerous processes of this nature,vegetable juices of any kind, moist sawdust, &c., cannot be exposed to the air, without immediately suffering a progressive change of colour and properties, during which oxygen is absorbed; these changes do not take place when water is excluded, or when the substances are kept at a low temperature, and it has been observed, that different woods require different degrees of heat, to affect the absorption of oxygen and consequently their eremacausis; the tendency to undergo this change is possessed in the highest degree by those substances which contain most nitrogen. The conditions which determine the commencement of decay, are of various kinds;—most woods, however, more, or less, oxidize slowly in the air, when simply moistened with water; in others, decay is retarded, or completely arrested, by all those substances which prevent fermentation, or putrefaction. Mineral acids, salts of mercury, aromatic substances, empyreumatic oils, and oil of turpentine,